Not applicable.
Titanium compounds, such as titanium nitride are finding increasing usage in a number of utilities, particularly in the production of electronic materials of construction for integrated circuits for computer chips.
Titanium nitride provides enhanced electrical conductivity for electronic circuits and exhibits excellent barrier properties for other metal depositions on silicon substrates. As a result, the electronics device fabrication industry has found increasing usage of titanium compound depositions for coatings prior to subsequent conductor metal depositions.
Techniques for titanium nitride deposition from tetrakis(dimethylamino)titanium (TDMAT) and tetrakis(diethylamino)titanium (TDEAT) are known in the literature. For instance, U.S. Pat. No. 5,139,825 discloses the deposition of titanium nitride from TDMAT or TDEAT in reaction with ammonia under chemical vapor deposition (CVD) conditions of 100 to 400xc2x0 C., preferably 150 to 300xc2x0 C., most preferably 200 to 250xc2x0 C., under reduced pressure and using an inert carrier gas, such as nitrogen or helium, to deposit titanium nitride on a heated substrate, such as a heated silicon containing substrate.
However, the deposition rate of titanium nitride has been highly variable and does not lend itself to repeatable, precise use in the electronic fabrication industry, where a multitude of silicon wafers are processed simultaneously, and many batches of wafers are processed consecutively. High yields of electronically acceptable wafers are necessary for the titanium nitride process to be acceptable commercially to the electronics fabrication industry. Additionally, the speed of deposition is critical to provide economic processing of titanium nitride coated wafers in the hundred plus step processing of blank silicon wafers to the final electrically acceptable individual integrated circuits produced by the electronics fabrication industry.
The problems of low depostion rate and variable deposition rate for titanium compounds deposited by CVD from titanium containing precursors is unexpectedly overcome by the process of the present invention by the addtion of amine additives and/or the removal of trace amounts of hydrocarbon impurities as will be set forth with greater detail below.
The present invention is a process for enhancing the chemical vapor deposition of titanium nitride from a titanium containing precursor selected from the group consisting of tetrakis(dimethylamino)titanium, tetrakis(diethylamino)titanium and mixtures thereof, reacted with ammonia to produce the titanium nitride on a semiconductor substrate by the addition of organic amines, such as dipropylamine, in a range of approximately 10 parts per million by weight to 10 percent by weight, preferably 50 parts per million by weight to 1.0 percent by weight, most preferably 100 parts per million by weight to 5000 parts per million by weight to the titanium containing precursor wherein prior to the reaction, said titanium containing precursor is subjected to a purification process to remove hydrocarbon impurities from the titanium containing precursor. It is shown that addition of small amounts of organic amines enhance the deposition rate of titanium nitride, while the presence of hydrocarbons, such as n-decane and analogous hydrocarbons, retard the deposition rate of titanium nitride.
The Present Invention is also a process for determining a predicted deposition rate of a batch of a titanium containing precursor in a chemical vapor deposition of a titanium containing compound on a substrate, comprising; analyzing the organic amine content of the batch to determine an analytical amine content, comparing the analytical amine content against an amine content standard and determining the predicted deposition rate from a deposition rate standard based upon the deviation of the analytical amine content from the amine content standard, wherein the predicted deposition rate is greater than the deposition rate standard when the analytical amine content is greater than the amine content standard and the predicted deposition rate is less than the deposition rate standard when the analytical amine content is less than the amine content standard.
The Present Invention is further a process for determining a predicted deposition rate of a batch of a titanium containing precursor in a chemical vapor deposition of a titanium containing compound on a substrate, comprising; analyzing the hydrocarbon content of the batch to determine an analytical hydrocarbon content, comparing the analytical hydrocarbon content against an hydrocarbon content standard and determining the predicted deposition rate from a deposition rate standard based upon a deviation of the analytical hydrocarbon content from the hydrocarbon content standard, wherein the predicted deposition rate is less than the deposition rate standard when the analytical hydrocarbon content is greater than the hydrocarbon content standard and the predicted deposition rate is greater than the deposition rate standard when the analytical hydrocarbon content is less than the hydrocarbon content standard.